You have had to make a lot of decisions lately. And dealing with your son's father certainly hasn't helped the anxiety levels. I think it's normal, this amount of nervousness and worry, as you have been out of the states for a long time. Try and think of the opportunities you will have for you and your son here, to actually meet some more new mothers and start making friends.
Yes, you will be living with your family, to help out with your Gram at first, but it doesn't mean you will be stuck there and it doesn't mean you have to be alone. You have done so well in these past few months, I (and I am sure everyone) can see the progress you have made navigating this world as a single mother. There is strength in that. Even though it's really hard to do, try to not worry about the what if's, or the rubbish that could happen once you get here, and try and focus on the positives of what coming back here can do for you and your son x